| Message ID | 20250403003532.412-1-chanho.min@lge.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | block: remove non-existent partition dev_t return from blk_lookup_devt | expand |
NAK. Don't do this. Md at least has a reason for doing this silly things as in the code as written in the 1990s where people did not know better. The dm-initwait code has no such excuse as it was written recently and explicitly ignored the rules to not use this early dev_t lookup code that is known to be broken. You now have to live with the fallout because you decided to you this broken code. Stop using it if you care. If there's one thing we need to do is to warn everyone in the Kconfig and boot time dmesg that dm-initwait is broken.
diff --git a/block/early-lookup.c b/block/early-lookup.c index 3fb57f7d2b127..3764dfb429c54 100644 --- a/block/early-lookup.c +++ b/block/early-lookup.c @@ -134,17 +134,9 @@ static dev_t __init blk_lookup_devt(const char *name, int partno) if (strcmp(dev_name(dev), name)) continue; - if (partno < disk->minors) { - /* We need to return the right devno, even - * if the partition doesn't exist yet. - */ - devt = MKDEV(MAJOR(dev->devt), - MINOR(dev->devt) + partno); - } else { - devt = part_devt(disk, partno); - if (devt) - break; - } + devt = part_devt(disk, partno); + if (devt) + break; } class_dev_iter_exit(&iter); return devt;
We encountered frequent boot failures while setting up a dm-verity rootfs with the following configuration, and found that this issue had been reported previously: root=/dev/dm-0 dm-mod.waitfor=/dev/mmcblk0p23 The error observed was: device-mapper: table: 254:0: verity: Data device lookup failed (-ENXIO) device-mapper: ioctl: error adding target to table Bisecting the issue revealed that this was a latent problem exacerbated by commit 238d991f054a ("dm: use fsleep() instead of msleep() for deterministic sleep duration"), after which the failures became more frequent. Further investigation pinpointed the root cause to a special case added in blk_lookup_devt() by commit 41b8c853a495 ("block: fix booting from partitioned md array") This commit modified blk_lookup_devt() to return a dev_t for non-existent partitions to support MD RAID booting when partitions are not yet available, e.g., for root=/dev/md_d0p1. While this addressed the MD issue, it deviates from the expected role of blk_lookup_devt(), which should return a dev_t only for existing block devices. Adding MD-specific logic to a common block layer function was a suboptimal approach, as it compromises the function's clarity and causes side effects, such as the dm-init failures seen with dm-verity. The MD RAID booting issue should ideally have been handled within the MD driver or boot logic (e.g., via a dedicated md_lookup_devt() function) rather than modifying a generic lookup function. This patch removes the non-existent partition dev_t return logic, restoring blk_lookup_devt() to its intended purpose. This resolves the dm-verity boot failures by ensuring accurate dev_t returns. If MD RAID booting still depends on this behavior in some setups, a regression may occur. In that case, the MD subsystem should implement a proper solution (e.g., specific lookup function) rather than relying on this workaround. Testers are encouraged to verify MD RAID booting with partitioned root devices (e.g., root=/dev/md_d0p1) to confirm. Signed-off-by: Chanho Min <chanho.min@lge.com> --- block/early-lookup.c | 14 +++----------- 1 file changed, 3 insertions(+), 11 deletions(-)